1. Field of the Invention
This invention relates to vibratory conveyors and, in particular, to improved vibratory conveyors for moving a variety of materials without inducing a vertical component of motion.
2. Description of the Background Art
Vibratory conveyors have been known and used for many years. In the usual type of vibrator conveyor, the material-carrying trough vibrated at an angle to the horizontal normally of the order of 45 degrees. The material conveyed is, in effect, bounced along the trough from one end to the other to effect the conveying action. Thus, for much of the travel the material is airborne, striking the material-carrying surface only long enough to be relaunched into the air in the direction of the discharge end of the conveyor.
The existence of vertical force and motion components offered many disadvantages. Because of the bouncing nature of the conveying actions, it was difficult for a worker standing alongside the trough to actually perform any work on the articles being conveyed. Because of the vertical motion, light particulate materials would tend to float upon launching and provide extremely dusty work environments. Because of the requirement of exceeding the acceleration of gravity, conveyors were load sensitive and not easily adapted to moving materials of various weight. By the very nature of repeated impacts of the material with the trough, substantial noise was contributed to the conveyance process.
One known commercial device attempts to eliminate many of the problems of vibratory conveyors which make use of vertical force and motion components. The device has a geared vibratory means at the inlet end of the trough, causing the vibratory forces to weaken as the distance from the vibratory means increases, and extreme bending and deflection may occur in the trough as the length of the trough is increased. Because of the inability to reposition the vibratory means along the length of the trough, it is not possible to suppress such deflection. It is impossible to position the vibratory means along the length of the trough because due to the gear size required to attain the necessary conveyance rates, it is not possible to pass the material-carrying trough through the vibratory means, which instead would have to be positioned either above or below the trough, thereby inducing a force couple and generating large stresses within the trough. In an arrangement with the vibrating means at the extreme end of the trough, large inertial forces act in tension and compression at the interface of the trough with the vibration generating means, inducing large stresses which lead to material failure of the trough. Means are also lacking for controlling the magnitude of the vibratory forces imparted to the trough while the apparatus is in operation.